Torpedo homing system

ABSTRACT

905,330 Steering torpedoes. CLEVITE CORPORATION. Aug. 31, 1955. [Sept. 7, 1954], No. 25073/55. Class 9(2). In a torpedo homing system acoustic signals from a target control the torpedo to circle in either direction alternately, reversing when reception ceases, so that the target is approached along a sinuous path which becomes progressively straighter as the torpedo swings through shorter ares. Electric signals from a transducer 30 feed a receiver circuit 31 having automatic gain control 32. When a signal is received, a relay 1 (a) actuates a speed control 34 to reduce the rate of turn of the torpedo as controlled by a gyro-azimuth motor 33, and (b) reduces gradually the gain in the amplifier of the receiver to diminish the sensitivity of the listening apparatus, so that it loses the target without going far beyond the true approach line. When the received signal is no longer strong enough, relay 1 operates again and (a) actuates a relay 2 to reverse the direction of the motor 33, (b) increases the speed of the motor 33, and (c) increases amplifier gain to increase sensitivity so that the torpedo is brought &#34; on target &#34; again with little loss of time. While the torpedo is &#34; on target &#34; the depth control is functioning, as in the prior art, and this control functions more effectively, as the torpedo is &#34; on target &#34; for a relatively larger proportion of the time.

Nov. 6, 1962. T. E. LYNCH TORPEDO HOMING SYSTEM 3 Sheets-Sheet 1 Filed Sept.- 7, 1954 R mm mN VU mE S A M o H T.-

W JATTOZNEY Nov. 6, 1962 4 5 9 1 t p e 0 I THOMAS E. LYNCH Nov. 6, 1962 T. E. LYNCH 3,062,166

TORPEDO HOMING SYSTEM Filed Sept. 7, 1954 3 Sheets-Sheet 3 CB A FIG. 4

GYRO RECEIVER RELAY AZIMUTH 2 MOTOR 30 i RELAY l I l I GAIN SPEED CONTROL CONTROL 32 34 FIG. 5

INVENTOR.

THOMAS E. LYNCH B ATTO NEY United States atent Filed Sept. 7, 1954, Ser. No. 454,350

r 3 Claims. ((11. 114-23) This invention relates to a torpedo homing system and method.

For the purpose of seeking out and destroying enemy surface ships, submarines and like targets a known technique involves launching a torpedo having electro-acoustic transducer apparatus for locating the target. Two general types of such transducer arrangements are used: the passive type, in which the torpedo transducer listens for acoustic signals originating at the target, such as due to the propellers; and the active or pulse-echo type, in which the torpedo transducer transmits through the water acoustic pulses which are reflected from the target, such reflections being picked up by the torpedo transducer. When initially launched, the torpedo after reaching the desired depth circles around and searches in all directions in azimuth. Upon locating a target, the torpedos course is thereafter controlled by the acoustic signals picked up by the torpedo transducer to direct the torpedo toward the target.

The present invention is directed to a novel'system and method for directing a torpedo toward a target under the control of acoustic signals picked up by the torpedo transducer apparatus which possesses certain distinct advantages over prior torpedo homing systems and methods employing the general searching technique above mentioned.

Accordingly, it is an object of the present invention to provide a novel and improved torpedo homing system and method. 7 v

It is also an object of this invention to provide a novel torpedo homing system and method which renders the torpedo less susceptible to being decoyed by targets other than the target first detected.

Also it is an object of this invention to provide a novel torpedo homing system and method which, after detection of a target and in moving toward the target, has an increased proportion of on target time and a reduced proportion of ofi target time, so that it is less likely to lose the target after once having detected it.

1 An additional object of this invention is to provide a novel torpedo homing system and method which enables more depth information to be received by the torpedo as a result of its increased on target time.

Another object of this invention is to provide a novel target seeking system and method for a torpedo which controls the movement of the torpedo toward the target until the final moment of impact.

A further object of the present invention is to provide a novel and improved torpedo homing system and method which is equally well adapted for either the passive or the pulse-echo type of transducer operation.

Another object of this invention is to provide a novel and improved torpedo homing system and method in which electro-acoustic transducers of conventional design may be used.

For the accomplishment of the foregoing purposes there is employed the torpedo homing system and method il 'lustrated in the accompanying drawings and pointed out in the following description.

In the drawings:

FIGURE 1 is a schematic diagram illustrating a prior art on-ofi system for directing a target-seeking torpedo toward the target;

FIGURE 2 is a schematic diagram illustrating the torpedo homing system and method of the present invention;

FIGURE 3 is a similar, more detailed view showing the present system and method; 1

FIGURE 4 is a family of curves showing the relationship between different torpedo transducer sensitivities and varying strengths of target signals; and

FIGURE 5 is a schematic block diagram showing in outline the components of the control system in the-torpedo in the present invention.

Referring first to FIGURE 1, this view illustrates a prior target seeking system and method which has been the subject of extensive development. In this system the torpedo, after being launched and descending to the desired search depth, is caused to turn in a circle (counterclockwise in FIG. 1) in order to search in all directions of azimuth. With the target positioned as shown, when the torpedo reaches the point 11 the target will just begin to be located within a predetermined tripping signal sensitivity pattern 11a of the electro-acoustic transducer apparatus on the torpedo. Typically, this pattern in azimuth would be an approximately triangular lobe having a wide rounded end away from the torpedo transducer. Any target located within or on the edge of this lobe will produce an acoustic signal of sufiicient magnitude to actuate the receiver circuit associated with the torpedo transducer. 7

In this prior art system when the target is first detected by. the torpedo transducer, the electrical signal developed by the transducer in response to the acoustic target signal actuates a suitable control which causes the torpedo to reverse the direction in which it is circling in azimuth. Thus, the torpedo now begins to circle clockwise in FIG. 1. As it turns in this direction the torpedo reaches point 12, where it loses the target since the tripping sensitivity lobe 12a of the torpedo transducerhas moved completely to the right of the target. Between the point 11, where the torpedo initially detected the target, and the point 12, where the torpedo lost the target, the torpedo is said to be on target, which means that the target is within the range and direction where its presence is detected acoustically by the torpedo transducer. Since the torpedo receives depth information only while it is in acoustic contact with the target, the depth control mechanism for the torpedo is arranged to be adjustable only while the torpedo is on target. When the torpedo loses the target (at point 12) the absence of a tripping signal at the torpedo transducer causes the latter to effect a reversal of the direction in which the torpedo is circling. Thus, the torpedo now starts again to circle counterclockwise in FIG. 1. Eventually the torpedo reaches point 13, where the target is again within the range of the tripping signal sensitivity pattern 13a of the torpedo transducer. Between the points 12 and 13 the torpedo is off target since its transducer is not receiving acoustic signals of tripping intensity from the target. In effect, therefore, during this time the torpedo has lost the target both in depth and azimuth.

The foregoing cycle is repeated, with the torpedo reversing the direction in which it is circling each successive time it picks up or loses the target. It will be apparent that with this technique the torpedo moves in the general direction of the target in a sinuous path. v This prior art system has certain disadvantages of considerable practical importance. The torpedo in moving toward thse target has a high proportion of on target time during which it is not detecting the target. This is so because the torpedo starts to turn away from the target as soon as the target first appears within the tripping sensitivity lobe of the torpedo transducer. Because of this high proportion of off target time, the torpedo is susceptible to being decoyed by other and spurious targets in the vicinity, rather than keeping after th target initially detected. Also, in many instances, insufiicient depth information is received during the brief on target increments of time to line the torpedo onto a depth collision line. This is particularly true if the torpedo initially is dropped relatively close to the target Or if the target is performing evasive maneuvers.

Another disadvantage of this prior system is that when the torpedo gets close to the target it tends to keep turning away from the target, and if it remained under the control of its onofi circuit the torpedo upon close approach would merely proceed to circle around the target indefinitely. To avoid this, after the torpedo has approached within a certain range close to the target, the oiT-turn circuit is inactivated and the torpedo turns toward the target. In its final movement toward hte target the torpedo is, in effect, running blind.

The present invention avoids these disadvantages by the provision of an arrangement in which the torpedo is kept on target as much as possible, rather than turning away from the target as soon 'as it comes n target, as in the above-described prior art system.

Referring to FIG. 2, assume that initially the torpedo is circling counterclockwise. When the torpedo reaches point 21 the target is located just on the left edge of the tripping sensitivity lobe 21a of the torpedo transducer. The acoustic signal from the target actuates the torpedo transducer, which in turn produces an electrical signal which causes the torpedo to continue to circle in the same direction. Therefore, the torpedo continues circling counterclockwise until it reaches the point 22, at which point the tripping sensitivity lobe 22a of the torpedo transducer has moved completely to the left of the target. During the entire time between points 21 and 22 the torpedo is continually on target, since the target is then within the tripping sensitivity lobe of the torpedo transducer.

In response to losing the target (at point 22), the cessation of a tripping signal at the transducer causes the latter to reverse the direction in which the torpedo is circling. Thus, the torpedo starts to turn clockwise in FIG. 2 and in so doing the target again is contacted by the torpedo transducer. When this happens, the transducer causes the torpedo to continue to circle clockwise until the torpedo has advanced to point 23, at which it again loses the target.

As this cycle repeates, the torpedo moves toward the target in a sinuous path, reversing its direction every time it loses the target and continuing to turn in the same direction as long as it is on target. Thus, the torpedo always seeking to either get on target or to remain on target, thereby achieving a maximum of on target time.

'With this arrangement, if the sensitivity of the transducer were to remain constant throughout the run, then the torpedo would swing through progressively wider arcs as it approached the target. It will be apparent that, other things being equal, the acoustic signal from the target will increase in amplitude as the target is approached. Referring to FIG. 4, if the tripping sensitivity of the transducer has the directional pattern in azimuth represented by lobe 4 and the target signal level at first positions of the target and the torpedo is represented by the line AA, then the transducer will be on target throughout the arc of movement of the torpedo represented by the angle a Oa which is defined by the intersections (a and a of the target signal line AA with the transducer sensitivity lobe 4 and the point at which the torpedo transducer is located. As the torpedo approaches the target, the target signal level would increase, and with the same transducer sensitivity (lobe 4) the torpedo would be on target throughout the arc of movement corresponding to the angle b O-b which is defined by the intersections (b and b of the target signal line BB with the transducer intensity lobe 4 and the point 0 at which the transducer is located. Upon closer approach of the torpedo toward the target, the target signal level would rise, and with the same transducer sensitivity (lobe 4) the torpedo would be on target throughout the arc of movement represented by angle c Oc which is defined by the intersections (c and c of the target signal line CC with the transducer sensitivity lobe 4 and the point 0 at which the torpedo transducer is located.

In order to avoid having the torpedo swing through progessively wider arcs as it approaches the target, which would unnecessarily slow down the overall rate of approach of the torpedo toward the target, the present invention has provision for reducing the sensitivity of the transducer apparatus on the torpedo as the torpedo approaches the target.

Theoretically, it might be possible to correlate the sensitivity at the torpedo transducer with the rate at which the target signal strength is increasing as the torpedo approaches the target such that the are through which the torpedo swings would be constant. Thus, assuming that the torpedo transducer has the sensitivity lobe 4 when it contacts the target which produces a signal represented by line AA, at this time, the torpedo would tend to swing through an arc whose angle is a -O-a throughout which arc the torpedo would be on target. Then, if, by the time the torpedo had approached closer to the target and the target signal had increased accordingly to BB, the transducer sensitivity had been reduced to the value represented by lobe 3, then the torpedo would tend to circle through an arc whose angle is b Ob defined by the intersections (b and In") of the target signal line BB with the intensity lobe 3 and the point at which the torpedo transducer is located. This are is identical to the previous arc defined by 'angle a Oa so that under these circumstances the torpedo will circle progressively through equal arcs of movement as it approaches the target.

While this is less objectionable than the first-mentioned possibility, in which the torpedo would swing through progressively wider arcs as it approaches the target, a more practical solution is to decrease the sensitivity at the torpedo transducer apparatus faster than the rate at which the target signal intensity increases as the torpedo approaches the target.

This action is illustrated in FIG. 4 as follows: Initially the torpedo transducer contacts the target when the transducer has a sensitivity represented by lobe 4 and the target signal strength is at the value represented by the line AA. At this time, the torpedo would tend to swing through an on target arc corresponding to angle a Oa After contacting the target, and as the torpedo now approaches the target, the target signal intensity trip level would increase to the value represented by the line B-B. At the same time the transducer sensitivity is reduced to the value represented by lobe 2. Accordingly, the torpedo would now tend to swing through the smaller arc corresponding to angle b Ob which angle is defined by the intersections (b and b of the target signal line BB with the transducer sensitivity lobe 2 and the position 0 0f the torpedo transducer.

However, this technique invloves the complication that the torpedo ultimately would lose the target because of the progressively decreased sensitivity of the torpedo transducer. Thus, by the time the target trip signal strength had increased to the value represented by line CC in FIG. 4 the transducer sensitivity would have decreased to the value represented by lobe 1, at which time the target would be completely beyond the reduced sensitivity range of the torpedo transducer.

In order to avoid this, the receiver circuit associated with the torpedo transducer has provision for rapidly increasing the gain or sensitivity toward the maximum as soon as the torpedo transducer loses the target. Thus,

aoearee if the target should be lost when the target signal strength is at the value represented by the line CC, as described above, the transducer sensitivity would rapidly be increased to the value sufiicient to again bring the torpedo on target.

The control circuit in the present system for accomplishing this result is outlined in block diagram form in FIG. 5. The electro-acoustic transducer 30 produces electrical signals which feed into a receiver circuit 31, which includes a multi-st-age amplifier whose gain is controlled by an automatic gain control 32. The gain control is under the control of relay 1, which in turn is actuated by an output signal from the receiver 31. Relay 1 also controls -a reversing relay, relay 2, which controls the direction in which the gyro azimuth motor 33 causes the torpedo to circle. Relay 1 additionally controls a speed control 34 associated with the gyro azimuth motor 33 to determine the rate at which the torpedo turns.

in the operation of this system, when the torpedo transducer 30 first locates the target, a target signal of tripping intensity is supplied through receiver 31 to actuate relay I. When this happens, relay 1 causes three things to happen:

(1) It actuates relay 2 to maintain the gyro azimuth motor 33 driving the torpedo in the same direction as it had been circling before locating the target;

(2) It actuates the speed control 34- to reduce the gyro azimuth motor 33 to a lower speed, so that the torpedo circles more slowly, now that it is on target; and

3) It actuates the gain control 32 to gradually reduce the gain in the amplifier in the receiver 31, thereby diminishing the sensitivity of the listening apparatus on the torpedo.

Whenever the torpedo transducer loses the target, either due to having turned through the target or due to reduced sensitivity in the receiver, relay 1 trips and does the following:

(1) It causes relay 2 to reverse the gyro azimuth motor 33 to thereby reverse the direction in which the torpedo circles;

(2) It causes the speed control 34 to bring the torpedo gyro azimuth motor up to full speed; and

(3) It causes the gain control 32 to rapidly bring the receiver 31 toward maximum sensitivity so as to again contact the target as soon as possible.

The overall result of this system is that the torpedo approaches the target in a sinuous path which becomes progressively straighter as the torpedo gets closer to the target because the torpedo swings through progressively shorter arcs in its approach to the target. This is indicated generally in FIG. 3, wherein the progressively decreasing sensitivity lobe patterns for the transducer receiver are somewhat simplified in order to facilitate an understanding of the action which takes place.

With the system of the present invention the torpedo is on target for a much greater proportion of time than possible heretofore. It stays on target as it approaches the target so that the present system can remain in operation to direct the torpedo in azimuth and depth until the instant of impact with the target, rather than letting the torpedo run blind after getting within striking range of the target. By virtue of its being on target longer, the present system enables a greater total of target signal information, both in azimuth and depth, to be supplied to the torpedo during the run of the torpedo. It is to be noted that in the present system the depth control mechanism for the torpedo is adjustable only while the torpedo is on target, as in the previous system, so that the increase in on target time is particularly valuable in that it increases the amount of depth information available. Consequently, the present system is particularly well adapted for close-target seeking and for coping with evasive maneuvering by the target. Because of the increase in azimuth and depth information available, the torpedo is less likely to lose the target and is less likely to be decoyed by other and spurious targets. Also, because the gain is reduced automatically after the torpedo comes on target any decoy is less likely to lure the torpedo oil? target.

While in the foregoing description and the accompanying drawings there has been disclosed a particular preferred embodiment of the present system and method, it is to be understood that various modifications, omissions and refinements which depart from the disclosed embodiments may be adopted without departing from the spirit and scope of the present invention. For example, the feature of reducing the gyro azimuth motor speed in response to coming on target may be eliminated, if desired, without appreciably detracting from the successful operation of the present invention.

I claim:

1. In combination on a torpedo, means for causing the torpedo to circle in either direction; electro-acoustic transducer means for receiving acoustic signals from a target; a receiver connected to the output of said transducer means and including amplifier means; a gain control for said amplifier means for selectively reducing or increasing the amplifier gain to vary correspondingly the sensitivity to acoustic signals of the transducer and receiver combination; and control means responsive to the output signals from said receiver and controlling the operation of said first-mentioned means and the operation of said gain control to:

(a) actuate said first-mentioned means to maintain the torpedo circling in the same direction and actuate said gain control to reduce the amplifier gain, both in response to the reception of acoustic signals which produce output signals of a predetermined amplitude or greater from the receiver, and

(b) actuate said first-mentioned means to reverse the direction in which the torpedo is circling and actuate the gain control to increase the amplifier gain, both in response to the cessation of reception by the transducer means of acoustic signals which produce output signals of said predetermined amplitude from the receiver.

2. The combination of claim 1, further characterized by means responsive to said control means and controlling the operation of said first-mentioned means to reduce the rate of turn at which the torpedo is circling while the transducer means is receiving acoustic signals which produce output signals from the receiver of said predetermined amplitude or greater.

3. In combination, a torpedo; means on the torpedo for causing the torpedo to circle in either direction; electro-acoustic transducer means on the torpedo for receiving acoustic signals from a target; a receiver connected to the output of said transducer means and including amplifier means; and means connected to the output of said receiver and controlling the operation of said firstmentioned means to actuate said first-mentioned means to maintain the torpedo circling in the same direction in response to the reception of acoustic signals which produce output signals from the receiver of predetermined value and to actuate said first-mentioned means to reverse the direction in which the torpedo is circling in response to the cessation of reception by the transducer means of acoustic signals which produce output signals from the receiver of said predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 2,588,382 Hammond Mar. 11, 1952 FOREIGN PATENTS 19,825 Great Britain Sept. 21, 1908 

